In a wireless communication system, a base station provides one or more coverage areas, such as cells or sectors, in which the base station can serve user equipment devices (UEs), such as cell phones, wirelessly-equipped personal computers or tablets, tracking devices, embedded wireless communication modules, or other devices equipped with wireless communication functionality.
In general, each coverage area could operate on one or more carriers each defining one or more ranges of frequency spectrum and having a respective downlink channel for carrying communications from the base station to UEs and a respective uplink channel for carrying communications from the UEs to the base station. Such carriers could be frequency division duplex (FDD), in which the downlink and uplink channels are defined as separate respective ranges of frequency, or time division duplex (TDD), in which the downlink and uplink channels are defined on a common range of frequency but are distinguished through time division multiplexing. Further, the downlink channel and uplink channel of each carrier could also be divided into respective sub-channels for carrying particular communications, such as one or more control channels for carrying control signaling and one or more traffic channels for carrying application-layer data and other traffic.
In an example system, for instance, the air interface could be divided over time into frames, and each frame could be divided over time into sub-frames, with each sub-frame defining two slots. The uplink and downlink channels could each be divided over their frequency bandwidth into sub-carriers that are grouped within each slot into resource blocks, with portions of each sub-frame further defining various control channels for signaling communication between the base station and UEs.
Further, when a base station receives uplink data from an end-user UE, the base station could route this data to one or more entities on a packet-switched network, and the base station could do so in a variety of ways. For instance, if the base station is a relay base station, then the base station could route the uplink data to the packet-switched network via a wireless backhaul connection. The wireless backhaul connection could be supported by an air interface between a donor base station and a relay UE served by the donor base station. In such an arrangement, uplink traffic from an end-user UE could pass from the end-user UE to the relay base station, from the relay base station to the relay UE, from the relay UE to the donor base station, and from the donor base station to a network entity. Alternatively, if the base station is a conventional, non-relay base station, then the base station could route the uplink data directly to the packet-switched network via a dedicated backhaul connection rather than via a wireless backhaul connection involving a donor base station and a relay UE.